Fluid-dash-pot buffer device.



F. .(LIURLOW. FLUID DASH POT BUFFER DEVICE.

APPLICATION FILED FEB. 28, 1907.

Patented June 10, 1913.

ATTORNEY UNITED STATES PATENT; OFFICE.

FLOYD C. FURLOW, OF MONTCLAIR, NEW JERSEY, ASSIGNOR TO OTIS ELEVATOR COM- IPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION" OF NEW JERSEY.

. Specification of Letters Patent.

Patented June 10, 1913.

Application filed February 28, 1907. Serial No. 359,883.

To all whom it may concern:

Be it known that I, F LOYD C. FUnLow, a citizen of the United States, residing at Montclair, in the county of Essex and State of-New Jersey, have invented a new and useful Improvement in Fluid-Dash-Iot Buffer Devices, of which the following is a specification.

My invention relates to safety buffers for elevators and one of its objects is the provision of simple and eflicient means for gradually retarding an elevator ear independently ofits operating apparatus so as to bring the car to rest gradually with mini.- 11111111 shock or jar.

A further object of the invention is the provision of resetting means for such bufier device-upon the release of the moving part of the elevator arranged to be brought into engagement with a moving part of said buffer device.

Other objects of the invention will appear hereinafter, the novel combinations of elements being set forth in the appended claims.

In the accompanying drawings, Figure 1 represents an elevator system illustrating the application of my invention; Fig. 2 is a vertical sectional elevation of my improved buffer device including the resetting means therefor; and Fig. 3 is a diagram illustrating the width of the opening restricting the fluid flow within the fluid-containing casing of the buffer device.

In general my invention comprises a buffer device shock absorber to overcome the inertia of a moving body in gradually stopping the same. In the accompanying drawing I have shown the buffer deviceat the lower limit of travel of an elevator car although it is obvious that it may be placed in the path of the counterweight or in the path of any other moving part which is desired to be stopped gradually'whether such part is in an elevator system or other apparatus.

In Fig. 1 two cushioning devices shown in detail in Fig. 2 are shown at the lower limit of the elevator well so as to be engaged by the elevator car as the same reaches or approaches its lower limit of travel, and by means of the combined retarding action of springs and a varying fluid pressure, the car is brought to a complete stop gradually and independently of the change valve or other manually controlled retarding mechanism although thecar may be descending at a high rate of speed.

Fig. 1 illustrates a typical hydraulic elevator of the well known plunger type, 1 designating an elevator car traveling along the usual guide rails, (not shown.) To the bottom of the car is securely attached the plunger 2 which is arranged to move up and down freelyin the main cylinder 18. The latter is supplied with fluid under pressure through the to-and-frcm pipe 16 from the pressure supply pipe 14 through the changevalve 17. 15 designates the discharge or ex- 1 haust pipe. The operation of the change valve 17 is controlled by means of a hand lever 10 in the car cooperating .Wltll the standing ropes 9,9, the sheave 11, the pinion l2, and the rack bar 13 in the well known manner. The standing ropes 9, 9 are fastened to the overhead beam 6 at 8, 8. The cable 4 is attached to the upper side of the car and extends upwardly over the sheave 5, mounted on the overhead beam 6 to the counterbalance weight 7. The counterweight partially balances the combined Weight of' the car and plunger. The cylinder 18 is of course closed at its lower end by a head 19 and it is evident that when the car operating lever 10 is moved in one direction or the other, the change valve 17 will be operated to open or closed position to allow the supply pressure to act on the plunger to lift the car, or to cause the unbalanced weight of the car and plunger and load to force the fluid out of the cylinder through the exhaust pipe 15.

Although in some instances only one buffer device would be sui'iicicnt, it would be preferable in stopping an elevator car to employ a plurality of them. In this instance I have shown two buffer devices 20" in Fig. 1 at the lower limit of travel of the elevator car, and so placed in respect thereto that each will be engaged by the bottom of the car near the lower limit of the cars travel.

Referring now to Fig. 2 which shows the details of one form of my invention, 21 designates a heavy compression spring loosely supported in a tube 22, and extending a short distance above the latter. The lower end of this tube is connected by the coupling 23 to the upper end of the tube 25. This coupling is screw-threaded at its ends to fit into the screw-threaded lower end of the tube 22 and the screw-threaded up er end of the tube 25, the middle portion 0 said coupling being of substantially the same diameter as said tubes. The lower portion of the tube 25 is provided with a p urality of perforations or passages 29 which may be staggered with respect to each other. The extreme lower end of the tube 25 is screwthreaded to the piston 26 which fits closely in the cylinder 31 and which is rovided with circumferential grooves 27. The piston 26 is cu -shaped thus forming an annular space etween the perforated portion of the tube 25 and the inner wall of said piston. The piston 26 is provided with an opening 28 in its bottom or lower port on, as viewed in Fig. 2. The cylinder 31 is of considerably larger diameter than the tube 25 and its lower end is provided with suitable supporting means, in this instance a standard 33, to which it is screw-threaded and which is provided with holes for bolts or other fastening means to securely hold the bufier device in roper position. The standard 33 is provi ed with a cylindrical recess 36 in its central portion, such recess being internally screw-threaded at its upper port-ion to receive the lower screw-threaded end of the tube 35. This tube 35 is open at both ends and extends upwardly into the cylinder 31 a predetermined distance in this instance nearly half its length. A long compression spring 32 is contained within the cylinder 31, and encircles the tube 35. The lower end of this spring rests on the annular portion of the standard 33 that projects into the lower end of the tube 31. The upper end of the spring engages the piston 26 and is held in substantially central position by means of an annular shoulder at-the lower end of said piston. 37 designates a long rod of peculiar form, preferably made of a single iece of steel, although it may be madeof ot er metal. The lowermost end of this rod is provided with an enlarged portion or head 34 so as to form an annular shoulder of larger diameter than the inner diameter of the tube 35 in which the rod loosely fits. The enlarged portion 34 lies in the recess 36 and is supported by the standard 33, such enlarged portion being rounded or spherically shaped on its lower side to form a pivot for the rod 37 which extends upwardly from the recess 36 loosely through the tube 35 and centrally through substantially the vertical axis of the tube 31 through the opening 28 in the piston 26. The rod 37 is of substantially uniform diameter between the head 34 and the broken line 'b a short'distance above the top of the tube '35. From I) to c the rod is tapered to a certain pitch, and from 0 to d the rod is tapered at a less pitch, and from d to a the rod is tapered very gradually. The remaining portion or the extreme upper tom of the piston or not.

noeaaoa end of the rod 37 is somewhat abruptly tapered to almost a point as shown. To the upper end of the cylinder 31 is secured a receptacle or oil well 38 of enlarged diameter over that of the cylinder 31. This receptacle is provided with a cap 48, and at its central inner portion with an annular flange, web or inward projection 39, thereby dividing the receptacle 38 into two chambers 47 and 41, communicating with each other through the annular passage 40. In this instance the cap 48 is bolted to the receptacle 38 and has a circular rid e 43 at its top to form a shallow basin or rip cup 42. The latter is provided with openings 44, 44 leading from this cup to the receptacle 38. If desired the cap 48 may be entirely closed, or in other words, the cap 48 need not be provided with the passages or holes 44, 44. A stop collar 46 is secured to the tube 25 in any suitable position which may be varied if desired, to limit the upward movement of the tube 25' and piston 26' so that the latter will occupy a predetermined position normally. In this instance, the cap 48 is provided with a downwardly and laterally extending collar 45 against which the stop 46 abuts to limit the upward movement of the tube 25 and piston 26, which upward movement is produced by the spring 32 when said piston and tube are free to move in the upward direction. The tube 31 and receptacle 38 are filled with some suitable liquid, such as water or oil, preferably up to the bottom of chamber 41 or up to the point a. While it may be feasible to use water or other liquid or even to have the dash-pot contain only air, I prefer to employ oil since it prevents rusting or corrosion, does not evaporate appreciably, and at the same time lubricates all the moving parts. Furthermore there is no possibility of the oil freezing and thereby rendering the device inoperative. V

The operation of the buffer device is as follows: As soon as the elevator car or other moving part desired to be stopped gradually, strikes the spring 21, the same is compressed and the tube 25 and the piston 26 started gradually downwardly. The spring 21 acts as a cushion for the tube or actuating device 25 and piston 26, and thus prevents them from receiving a sudden blow, but on the contrary permits them to be started up gradually. The oil contained within the cylinder 31 is now forced to flow through the annular passage 28 and the perforations 29 to the upper side of the pistion of the piston 26, the area of the annular passage 28 will be substantially the same whether the rod is in exactly central position with respect to the opening in the bot- Since the rod .37 projects through the opening in the piston,

it .will be seen that the flow of oil is restricted in its movement from the lower side of the piston to the upper side. As the piston 26 continues to move downwardly the. retardation to the flow of oil gradually increases by reason of the gradually increasing diameter of the rod 37. This retardation increase continues gradually to the point 01 when the rate of increase of retardation becomes greater. This increase continues from the point (Z 'to the point 0 where the rate again increases. At the point I) the rod 37 is of substantially thesame diameter as the opening in the lower portion of the piston 26, or of slightly less diameter to prevent binding or sticking of the piston to the rod at this point. then the piston 26 reaches the,- 'point b any further downward movementof the-piston is prevented since the oil under the piston has no outlet and the nature of the fluid does not permit of compression since it is substantially nonelastic. If the point 7) is of slightly less diameter than the opening 28, the piston 26 may finally reach the upper end of the tube 35 which will then absolutely limit the downward movement of the piston. As soon as the elevator car or the moving partwhich has engaged the spring 21, is moved away from the buffer device, the piston and attached mechanism is forced upwardly by the spring 32 to reset or restore the moving parts to their normal or original positions as shown in the drawings, the stop-collar 46 being then in positive engagement with the cap collar 45 to prevent an excessive upward movement of the tube 25, the spring 32 being still slightly under compression. During the upward movement of the piston 26 from its lowermost limit of travel, the oil above the piston may either immediately flow through the passage 28, or such oil above the piston is first lifted until a. passage through the bottom of the piston is formed when the vacuum below the piston will cause the oil to immediatelypass beneath the piston from above. The passages or perforations 29 are sufliciently numerous to allow a free flow of oil through the same in either direction. The chamber 47 serves the purpose of an expansion chamber for the oil since it is necessary to make provision for the change in volume of the oil due to changes in temperature and for the changes in height of the oil due to displacement by the tube 25. The chamber 47 also forms a space for receiving the oil when it is forced upwardly .as the spring 32 first starts the piston 26 in its upward direction from its lowermost position. The drip cup 42 catches any excess of oil on the tube 25 and returns it by way of the passages 44, 44, to the chamber 41.

It should be noted that although the extreme upper end of the tapered memher 37 is shown projecting through the o mng through the piston, it is obvious tat in some instances the member 37 may be made shorter or the; piston 26 normally above the same. In such event the piston will always slide over the rod 37 nevertheless, since the tube, 35 holds the rod 37 substantially coincident, in this-instance, with the-axis of the cylinder 31. In order to obviate the necessity of too reat a refinement of the alinement of the ro 37 and the opening in the piston, the rod is allowed to have a limited lateral play in the tube 35. In such event it is evident that when the piston is forced downwardly, the fluid beneath the same will find its way to the underside of the rod 37 and tend to force the same out of the tube 35, but' this is prevented by the shoulder 34. Even when the rod 37 fits tightly within the tube 35, unless secured thereto, the rod 37 .will be drawn upwardly by the fluid as it flows through the restricted passage 28. 'In other words, as the fluid flows from the underside of the piston to the upper side it tends to carry the rod with it but is prevented from doing so, in this instance, by the shoulder 34 striking against the lower end of the tube 35. If desired the pivot in the recess 36 may be a fixed one to prevent upward movement of the rod 37, or said rod may be fixed rigidly to the standard 33, in which case the tube 35 may be omitted. It is preferred, however, to secure the best results in practice, to employ substantially the structure shown.

The rate of retardation is not a constant owing tothetapered form of the rod 37,. As the piston is forced downwardly the rate ofretardat-ion increases gradually, and after the piston reaches the point. opposite the broken line d, the rate of increase of retardation becomes greater due to the increased tapering of the rod 37. At 0 the retardation becomes still greater, and at the point I) the retardation is at its maximum as hereinbefore explained.

Fig. 3 is a diagram illustrating the width of the passage 28 between the rod 37 and the walls of the opening through the piston for diiferont positions of the piston. The length of the diagram represents the length of travel or the stroke of the piston. The width of the diagram at any point represents the width of the passage 28 for a corresponding position of piston. The righthand side of the diagram is a vertical straight line to represent the path of any point in the wall of the opening through the piston, and the left-hand side is inclined to correspond to the adjacent tapered or inclined surface of the rod 37. The straight line from a to (Z is slightly inclined to correspond to the tapered portion of the rod 37 between a and cl, the inclination from cl to c is greater to represent the increased &

pitch in the taper of the rod from c to d,- and the inclination of the line 0 b is still greater to represent the part of the rod 37 between 6 and a which has the greatest pitch. As the diagram indicates the gradual decrease in the width of the annular opening 28 as the piston moves down, it also serves to indicate the gradual restriction to the flow of fluid and consequent retardation from the point a, where the retardation is slight, to the point Z), Where the retardation is at a maximum, and the piston is finally stopped by the entire closing of the passage 28 or by the striking of the piston against the tube 35;

While I have described my device in connection with an elevator system, there are many uses to which my invent-ion could be put to great advantage. I have shown a preferred construction and illustrated and described one practical use to which it may be put. It is obvious, however, that a person skilled in the art may make various changes in the details and arrangement of parts to suit dilierent conditions without departing from the spirit and scope of my invention, and I desire, therefore, not to be limited to the precise construction and arrangement of parts disclosed.

Having thus fully described my invention, what I claim as new and desire to have protected by Letters Patent of the United States is 1. The combination with a receptacle for containing liquid, of an expansion chamber connected at or near one end of said receptacle, a piston movable in said receptacle, a tube connected to said piston and having perforations ailording passages between said expansion chamber and said receptacle through an opening in said piston, and

menace means within said receptacle for variably restricting the flow of fiuid through said opening in the piston,

2. The combination with a cylinder, of a tube of smaller diameter than the cylinder, fixed to one end thereof, and extending longitudinally into the cylinder, a rod of less diameter than the tube and within the same, having a portion thereof tapered toward the other end of the cylinder, means for preventing said rod from being forced out of said tube by fluid-pressure, a piston movable in said cylinder, said piston having an opening for receiving the tapered portion of said rod, an expansion chamber connected to said cylinder, a perforated tube connected to said piston at one side thereof, and projecting out of said expansion chamber, a spring acting on the other side of said piston to move the latter away from said rod, and a stop for limiting such movement.

3. The combination with a receptacle for containing liquid, of an expansion chamber connected at or near one end of said receptacle, a piston movable in said receptacle, a tube connected to said piston and having perforations affording passages between said expansion chamber and said receptacle through an opening in said piston, and means Within said receptacle for variably restrictin the flow of fluid through said opening in the piston comprising a rod, loosely supported in the receptacle to allow a slight lateral play of the rod in the same.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

FLOYD C. FURLOVV.

Witnesses:

W. W. LIGHTH-IPE, J. H. VAN ALSTYNE. 

